The present invention relates to an anchoring means for anchoring by a bonding mass in a drilled hole in a concrete part.
More particularly, it relates to an anchoring means which each have a threaded bolt with an expansion cone surrounded by an anchoring sleeve which can be expanded by the expansion cone.
It is known, for anchoring a threaded rod by means of a bonding mass, to form a drilled hole which has an undercut in the region of the bottom of the drilled hole. Such an anchorage is described in DE-A-13 516 866. The fixing of this known anchoring means is effected in that there is pushed into the drilled hole a glass ampoule which contains a bonding mass of polyester resin, a hardener and additives. On insertion of the anchoring means into the drilled hole, the glass ampoule is destroyed and the components of the bonding mass are activated by mixing. After the bonding mass has hardened, the anchoring means is rigidly bonded and anchored in the drilled hole. The anchorage depends essentially on the adhesive bond between the bonding mass and the wall of the drilled hole. This bond, however, is reduced considerably if a crack runs through the anchorage point. Through the enlargement of the drilled hole as a result of the crack, the bonding mass becomes detached from the wall of the drilled hole so that in the straight shaft part of the anchoring means, only limited retaining forces still obtain. The known anchoring means has, however, a conical widening in the region of the undercut of the drilled hole, so that greater retaining forces still obtain there. These depend on the form of the undercut and on the proportion of the undercut region to the total length of the hole.
The production of an undercut drilled hole requires special tools and generally also a greater expenditure during the production of the drilled hole. For this reason, experiments have already been undertaken to reduce the sensitivity to cracks by means of special configurations of the bonded anchoring means in cylindrical drilled holes. Thus, for example, it was proposed to provide the threaded bolt of the anchoring means with a cone which, by means of a coating, is capable of sliding with respect to the hardened bonding agent core. The result which is intended to be achieved thereby is that the threaded bolt settles in the bonding agent core to compensate for the widening of the crack. Such settlement can of course only be achieved if the entire threaded bolt detaches itself with respect to the hardened bonding agent core. This of course results in a considerable reduction in the holding value. Moreover, the bonding agent core is not very stable under pressure, so that even with relatively limited forces, pulling of the threaded bolt through the bonding agent core occurs.
The problem on which the invention is based is that of providing an anchoring means for anchoring by means of a bonding mass in a cylindrical drilled hole in a concrete part, which has high safety reserves in the case of anchoring in the zone subject to tensile forces, and the widening of the drilled hole which arises as a result of the formation of cracks.